At one time, automatic telephone exchanges were typically limited to providing "plain ordinary telephone service", sometimes referred to as POTS. With POTS, a telephone user may place or initiate a telephone call by dialling a telephone number which identifies the telephone set of another telephone user with whom communication is desired. The telephone user who initiates the call is referred to as a calling party, and the telephone user for whom the call is intended is referred to as a called party. A telephone call involves various elements of the telephone exchange. These elements operate in concert to provide a communication path for the duration of the communication, be it with the called party or alternately with other means to inform the calling party that communication with the party designated by the dialled telephone number is unavailable. Depending upon prevailing conditions of the moment, each telephone call follows a well known progression of events and is termed a call progress. A call progress is initiated when the telephone user actuates a telephone terminal apparatus. This actuation is usually referred to as going OFF HOOK. This event of going OFF HOOK is usually followed by some action being performed by the user. If the user is the calling party, the user indicates an identity of the called party by pressing or dialling digits associated with the called party's telephone set, that is the called party's telephone number. Such action will usually cause one of three typical call progresses in the telephone system, which are briefly summarized as follows:
1) The called party answers by going OFF HOOK, in response to ringing of the called party's telephone set, whereby the calling party is provided with a real time communication or conversation with the called party; PA1 2) The called party will not answer, as the called party is unresponsive to ringing or the called party is already using his telephone set, in which case the calling party has no recourse but to terminate the progress of the call by going ON HOOK; and PA1 3) The telephone call is connected to a voice service feature or a telephone answering machine associated with the called party, which answers on behalf of the called party. In this case, the calling party is usually urged to leave a message for the called party, whereby the calling party may have a delayed communication transmitted to the called party. PA1 a) responding to an incoming telephone call from a calling party by initiating a call toward a telephone set of a called party; PA1 b) in an event of the call having been intercepted, transmitting an indication of the intercepted call to the called party's telephone set; and PA1 c) in response to an occurrence of a predetermined signal from the called party's telephone set, prior to a cessation of the intercepted call, altering the call to include the called party. PA1 u) causing an indication of the call screening feature at a telephone set, in response to the call screening feature having been invoked at the telephone set; PA1 v) in an event of the telephone set being called, while the call screening feature is invoked intercepting the call at one of an attendant position and a voice features server; PA1 w) if the called telephone set is OFF HOOK, transmitting a signal for indicating an occurrence of an intercepted call, to the called telephone set. If the called telephone set is ON HOOK, progress of the call is altered to include a link with the intercepted call, whereby the intercepted call is audible at the called party's telephone set.
A primary function of the voice services feature and the telephone answering machine is that of providing an opportunity for a calling party to leave a message for subsequent receipt by a called party. The first such message service was provided by a service person or a special operator who arranged to intercept telephone calls on behalf of a subscriber to the service. This personal service is relatively expensive and consequently, it has never became commonplace in the day-to-day activities of most telephone users. However recently, machine implementations of telephone answering and voice messaging services have become relatively inexpensive to use. Telephone answering service is available by means of any of various user purchasable answering machines for use with individual telephone terminal apparatus. Alternately more sophisticated voice messaging services are available by access to a voice services feature associated with a telephone key system or a telephone exchange. Voice services provided in this manner are often referred to as centralized voice feature services. Examples of centralized voice feature services may be provided with telephone equipment identified by the trademarks of Norstar and Meridian, manufactured by Northern Telecom Limited.
In addition to the function of capturing voice messages from calling parties, a secondary function of the answering machine is that of a call screening function. The typical telephone answering machine is connected to the telephone line and is arranged to answer an incoming telephone call after the occurrence of several ringing signals. When the telephone call is answered, the callers voice is usually made audible via a loudspeaker in the answering machine provided for this purpose. In the event that the called party is physically present, but is unable to answer or has chosen not to answer the telephone immediately, the called party's identity and purpose for calling may become audibly apparent to the called party. In this event, the called party may choose to communicate directly with the calling party, in a real time conversation, simply by going OFF HOOK Some examples of a series of telephone answering machines, manufactured by Northern Telecom Limited, are identified by the trademark Symphony 6000, Symphony 7000 and Symphony 8000.
In contrast, if a called party is a user of a centralized voice services feature, there is no local telephone answering machine and the called party is unable to hear any message being deposited. The centralized voice services feature is not physically associated with the called party's telephone line and hence the called party is not made aware of the calling party, except by subsequent access to the centralized voice services feature. Hence, it is at some later time that the called party may be advised of the call and possibly of the caller's intent.